Since the advent of a resist for a KrF excimer laser (248 nm), an image forming method called chemical amplification has been used as a resist image forming method so as to compensate for sensitivity reduction caused by light absorption. For example, an image forming method by positive-type chemical amplification is an image forming method in which an acid generator in an exposed area is decomposed by exposure to generate an acid, an alkali-insoluble group is converted into an alkali-soluble group by using the generated acid as a reaction catalyst in post exposure baking (PEB), and the exposed area is removed by alkali development. The positive-type image forming method using the chemical amplification mechanism currently has become a mainstream.
Further, with an aim to further shorten the wavelength and thereby to obtain higher resolution, a so-called immersion method of filling a high refractive index liquid (hereinafter, also referred to as “immersion liquid”) between a projection lens and a test sample has been known. For example, as a positive resist composition for the immersion exposure, Japanese Patent Application Laid-Open No. 2007-230913 discloses a positive resist composition that contains a photo-acid generator having an amino group in the cationic moiety.
However, in the above described positive-type image forming method, an isolated line or dot pattern may be well formed, but the shape of a pattern may be easily deteriorated when an isolated space or fine hole pattern is formed.
Therefore, in response to the demand for further refinement of a pattern, a technology of resolving a negative pattern instead of the positive-type as the current mainstream, in which an organic-based developer is used for a resist film obtained by a chemical amplification resist composition, has recently been known. For example, as such a technology, Japanese Patent Application Laid-Open No. 2011-22560 discloses a technology in which a basic compound or an ammonium salt compound whose basicity is decreased upon irradiation with an actinic ray or radiation is used in a negative pattern forming method through an organic-based developer using an immersion method.
However, more recently, a demand for refinement of an isolated space pattern has been rapidly increased. Accordingly, particularly when a ultrafine isolated space pattern (with a space width of, for example, 60 nm or less) is formed on a resist film, it is required to further improve a line width roughness (hereinafter, also referred to as LWR), and a mask error enhancement factor, hereinafter referred to as “MEEF” (capability of fully realizing a pattern formed by an unexposed area and an exposed area as a resist pattern in a mask).
Also, it is required that generation of particles hardly occurs even when a resist solution is stored with elapse of time, and as a result, a good pattern may be formed.
The present invention has been made in consideration of the aforementioned problem, and an object thereof is to provide a pattern forming method, a method for manufacturing an electronic device using the pattern forming method, and an electronic device, in which in the formation of an ultrafine isolated space pattern (with a space width of, for example, 60 nm or less), a line width roughness performance and a mask error enhancement factor are excellent, and also generation of particles may be inhibited even during storage of a resist solution with elapse of time, thereby allowing a good pattern to be formed. Particularly, the object is to provide a pattern forming method suitable for immersion exposure, a method for manufacturing an electronic device using the pattern forming method, and an electronic device.